Facile Oxidative Cleavage of 4-O-Benzyl Ethers with Dichlorodicyanoquinone in Rhamno- and Mannopyranosides

Abstract

On exposure to dichlorodicyanoquinone in wet dichloromethane at room temperature, equatorial 4-O-benzyl ethers are removed with moderate selectivity in the presence of other benzyl ethers in glycopyranosides and glycothiopyranosides.

An Easy and Versatile Approach for the Regioselective De‐O‐benzylation of Protected Sugars Based on the I2/Et3SiH Combined System

“…[16] The primary positions can be de-Obenzylated (and concomitantly triethylsilylated) with excellent regioselectivity on prolonged exposure of benzylated mono-, di-and trisaccharides to the Et 3 SiH/A C H T U N G T R E N N U N G [Co 2 (CO) 8 ] combined system, at high temperature under a CO atmo-A C H T U N G T R E N N U N G sphere. [17] Acetolysis is another approach that often leads to selective de-O-benzylation (and concomitant acetylation) of the primary positions, but in this case undesired cleavage of glycosidic bonds might occur.…”

Synthesis of the Antigenic Tetrasaccharide Side Chain from the Major Glycoprotein of Bacillus anthracis Exosporium.

“…41 The moderate yield of 27 is attributable to the previously reported problem of the competing debenzylation reactions in the course of the DDQ promoted cleavage of 2-naphthylmethyl/p-methoxyphenyl ethers. 33 To overcome this difficulty the mixture of debenzylated byproducts of the 2-naphthylmethyl deprotection reaction was benzylated under standard conditions to give 28, suitable for further transformations to the target molecule through the same routes as 27. Final removal of the benzyl protecting groups and transformation of azide moiety to the amine was achieved by application of sodium in liquid ammonia to the mixture of 27 and 28.…”

Cyanopivaloyl Ester in the Automated Solid-Phase Synthesis of Oligorhamnans

“…The synthesis of the required dirhamnosyl building blocks is depicted in Scheme 2 and started by coupling imidate donor 14 (12) and acceptor 15 (26)/ 16 12 using a catalytic amount of TfOH. This led to disaccharides 17 and 18 , which could both be purified by crystallization from hot ethanol.…”

“…Compound 15 (26) (4.96 g, 11.52 mmol, 1.0 equiv) and imidate donor 14 (7.56 g, 13.32 mmol, 1.2 equiv) were coevaporated twice with anhydrous toluene under an argon atmosphere, after which they were dissolved in dry DCM (56 mL). The mixture was stirred on activated molecular sieves for 20 min at RT and then cooled to 0 °C.…”